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From: Catalin Marinas <catalin.marinas@arm.com>
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	kvm@vger.kernel.org, Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	dri-devel@lists.freedesktop.org,
	Linux Memory Management List <linux-mm@kvack.org>,
	"open list:KERNEL SELFTEST FRAMEWORK"
	<linux-kselftest@vger.kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Leon Romanovsky <leon@kernel.org>,
	linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org,
	Dmitry Vyukov <dvyukov@google.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Evgenii Stepanov <eugenis@google.com>,
	linux-media@vger.kernel.org,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
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	Lee Smith <Lee.Smith@arm.com>,
	Alexander Deucher <Alexander.Deucher@amd.com>,
	Andrew Morton <akpm@linux-foundation.org>,
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	Robin Murphy <robin.murphy@arm.com>,
	Christian Koenig <Christian.Koenig@amd.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Subject: Re: [PATCH v15 00/17] arm64: untag user pointers passed to the kernel
Date: Fri, 24 May 2019 11:11:40 +0100
Message-ID: <20190524101139.36yre4af22bkvatx@mbp> (raw)
In-Reply-To: <ffe58af3-7c70-d559-69f6-1f6ebcb0fec6@oracle.com>

On Thu, May 23, 2019 at 03:49:05PM -0600, Khalid Aziz wrote:
> On 5/23/19 2:11 PM, Catalin Marinas wrote:
> > On Thu, May 23, 2019 at 11:51:40AM -0600, Khalid Aziz wrote:
> >> On 5/21/19 6:04 PM, Kees Cook wrote:
> >>> As an aside: I think Sparc ADI support in Linux actually side-stepped
> >>> this[1] (i.e. chose "solution 1"): "All addresses passed to kernel must
> >>> be non-ADI tagged addresses." (And sadly, "Kernel does not enable ADI
> >>> for kernel code.") I think this was a mistake we should not repeat for
> >>> arm64 (we do seem to be at least in agreement about this, I think).
> >>>
> >>> [1] https://lore.kernel.org/patchwork/patch/654481/
> >>
> >> That is a very early version of the sparc ADI patch. Support for tagged
> >> addresses in syscalls was added in later versions and is in the patch
> >> that is in the kernel.
> > 
> > I tried to figure out but I'm not familiar with the sparc port. How did
> > you solve the tagged address going into various syscall implementations
> > in the kernel (e.g. sys_write)? Is the tag removed on kernel entry or it
> > ends up deeper in the core code?
> 
> Another spot I should point out in ADI patch - Tags are not stored in
> VMAs and IOMMU does not support ADI tags on M7. ADI tags are stripped
> before userspace addresses are passed to IOMMU in the following snippet
> from the patch:
> 
> diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
> index 5335ba3c850e..357b6047653a 100644
> --- a/arch/sparc/mm/gup.c
> +++ b/arch/sparc/mm/gup.c
> @@ -201,6 +202,24 @@ int __get_user_pages_fast(unsigned long start, int
> nr_pages
> , int write,
>         pgd_t *pgdp;
>         int nr = 0;
> 
> +#ifdef CONFIG_SPARC64
> +       if (adi_capable()) {
> +               long addr = start;
> +
> +               /* If userspace has passed a versioned address, kernel
> +                * will not find it in the VMAs since it does not store
> +                * the version tags in the list of VMAs. Storing version
> +                * tags in list of VMAs is impractical since they can be
> +                * changed any time from userspace without dropping into
> +                * kernel. Any address search in VMAs will be done with
> +                * non-versioned addresses. Ensure the ADI version bits
> +                * are dropped here by sign extending the last bit before
> +                * ADI bits. IOMMU does not implement version tags.
> +                */
> +               addr = (addr << (long)adi_nbits()) >> (long)adi_nbits();
> +               start = addr;
> +       }
> +#endif
>         start &= PAGE_MASK;
>         addr = start;
>         len = (unsigned long) nr_pages << PAGE_SHIFT;

Thanks Khalid. I missed that sparc does not enable HAVE_GENERIC_GUP, so
you fix this case here. If we add the generic untagged_addr() macro in
the generic code, I think sparc can start making use of it rather than
open-coding the shifts.

There are a few other other places where tags can leak and the core code
would get confused (for example, madvise()). I presume your user space
doesn't exercise them. On arm64 we plan to just allow the C library to
tag any new memory allocation, so those core code paths would need to be
covered.

And similarly, devices, IOMMU, any DMA would ignore tags.

-- 
Catalin

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  reply index

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06 16:30 Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 01/17] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2019-05-29 14:49   ` Khalid Aziz
2019-05-06 16:30 ` [PATCH v15 02/17] arm64: untag user pointers in access_ok and __uaccess_mask_ptr Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 03/17] lib, arm64: untag user pointers in strn*_user Andrey Konovalov
2019-05-22 10:41   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 04/17] mm: add ksys_ wrappers to memory syscalls Andrey Konovalov
2019-05-22 10:56   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 05/17] arms64: untag user pointers passed " Andrey Konovalov
2019-05-22 11:49   ` Catalin Marinas
2019-05-22 21:16     ` Evgenii Stepanov
2019-05-23  9:04       ` Catalin Marinas
2019-05-24  4:23         ` Evgenii Stepanov
2019-05-24 15:41   ` Andrew Murray
2019-05-25  9:57   ` Catalin Marinas
2019-05-27  9:42   ` Catalin Marinas
2019-05-27 14:37   ` Catalin Marinas
2019-05-28 14:54     ` Andrew Murray
2019-05-28 15:40       ` Catalin Marinas
2019-05-28 15:56         ` Dave Martin
2019-05-28 16:34           ` Catalin Marinas
2019-05-29 12:42             ` Dave Martin
2019-05-29 13:23               ` Catalin Marinas
2019-05-29 15:18                 ` Dave Martin
2019-05-28 23:33         ` Khalid Aziz
2019-05-29 14:20           ` Catalin Marinas
2019-05-29 19:16             ` Khalid Aziz
2019-05-30 15:11               ` Catalin Marinas
2019-05-30 16:05                 ` Khalid Aziz
2019-05-30 16:57                   ` Catalin Marinas
2019-05-28 13:05   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 06/17] mm: untag user pointers in do_pages_move Andrey Konovalov
2019-05-22 11:51   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 07/17] mm, arm64: untag user pointers in mm/gup.c Andrey Konovalov
2019-05-22 11:56   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 08/17] mm, arm64: untag user pointers in get_vaddr_frames Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 09/17] fs, arm64: untag user pointers in copy_mount_options Andrey Konovalov
2019-05-22 12:09   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 10/17] fs, arm64: untag user pointers in fs/userfaultfd.c Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 11/17] drm/amdgpu, arm64: untag user pointers Andrey Konovalov
2019-05-07 16:43   ` Kuehling, Felix
2019-05-06 16:30 ` [PATCH v15 12/17] drm/radeon, arm64: untag user pointers in radeon_gem_userptr_ioctl Andrey Konovalov
2019-05-07 16:44   ` Kuehling, Felix
2019-05-06 16:30 ` [PATCH v15 13/17] IB, arm64: untag user pointers in ib_uverbs_(re)reg_mr() Andrey Konovalov
2019-05-06 19:50   ` Jason Gunthorpe
2019-05-07  6:33     ` Leon Romanovsky
2019-05-06 16:31 ` [PATCH v15 14/17] media/v4l2-core, arm64: untag user pointers in videobuf_dma_contig_user_get Andrey Konovalov
2019-05-24 13:13   ` Mauro Carvalho Chehab
2019-05-06 16:31 ` [PATCH v15 15/17] tee, arm64: untag user pointers in tee_shm_register Andrey Konovalov
2019-05-06 16:31 ` [PATCH v15 16/17] vfio/type1, arm64: untag user pointers in vaddr_get_pfn Andrey Konovalov
2019-05-06 16:31 ` [PATCH v15 17/17] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2019-05-22 14:16   ` Catalin Marinas
2019-05-31 14:21     ` Andrey Konovalov
2019-05-31 16:22       ` Catalin Marinas
2019-05-17 14:49 ` [PATCH v15 00/17] arm64: untag user pointers passed to the kernel Catalin Marinas
2019-05-20 23:53   ` Evgenii Stepanov
2019-05-21 18:29     ` Catalin Marinas
2019-05-22  0:04       ` Kees Cook
2019-05-22 10:11         ` Catalin Marinas
2019-05-22 15:30           ` enh
2019-05-22 16:35             ` Catalin Marinas
2019-05-22 16:58               ` enh
2019-05-23 15:21                 ` Catalin Marinas
2019-05-22 20:47               ` Kees Cook
2019-05-22 23:03                 ` Evgenii Stepanov
2019-05-22 23:09                   ` enh
2019-05-23  7:34                     ` Catalin Marinas
2019-05-23 14:44                 ` Catalin Marinas
2019-05-23 15:44                   ` enh
2019-05-23 17:00                     ` Catalin Marinas
2019-05-23 16:38                   ` Kees Cook
2019-05-23 17:43                     ` Catalin Marinas
2019-05-23 21:31                       ` Kees Cook
2019-05-24 11:20                         ` Catalin Marinas
2019-05-28 17:02                         ` Catalin Marinas
2019-06-02  5:06                           ` Kees Cook
2019-05-22 19:21             ` Kees Cook
2019-05-22 20:15               ` enh
2019-05-23 15:08               ` Catalin Marinas
2019-05-23 17:51         ` Khalid Aziz
2019-05-23 20:11           ` Catalin Marinas
2019-05-23 21:42             ` Khalid Aziz
2019-05-23 21:49             ` Khalid Aziz
2019-05-24 10:11               ` Catalin Marinas [this message]
2019-05-24 14:25                 ` Khalid Aziz
2019-05-28 14:14                   ` Andrey Konovalov
2019-05-29  6:11                     ` Christoph Hellwig
2019-05-29 12:12                       ` Catalin Marinas
2019-05-30 17:15                     ` Catalin Marinas
2019-05-31 14:29                       ` Andrey Konovalov
2019-05-31 16:19                         ` Catalin Marinas
2019-05-31 16:24                           ` Andrey Konovalov
2019-05-31 16:46                             ` Catalin Marinas
2019-05-21 18:48   ` Jason Gunthorpe
2019-05-22 13:49     ` Dave Martin
2019-05-23  0:20       ` Jason Gunthorpe
2019-05-23 10:42         ` Dave Martin
2019-05-23 16:57           ` Catalin Marinas
2019-05-24 14:23             ` Dave Martin

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